Manufacture of stannic chloride



July 14, 1936. w. J. BUTTFIELD MANUFACTURE OF STANNIC CHLORIDE 2 Sheets-Sheet l Filed Jan. 1l, 1953 lNvENToR I W/LL/AMI UTTF/ELD MSSS ATTORNEYS July 14, 1936- w. J. BUTTFIELD MANUFCTURE OF STANNIC CHLORDE Filed Jan. ll, 1953 2 Sheets-Sheet 2 NWN INVENTOR W/LL/AMJEUTTF/E'L Y @J4-,balm M ATToRNEYj Patented July 14, 1936 PATENT OFFICE MANUFACTURE OF STANNI CHLORIDE William J. Butteld, North Plainield, N. J., as-

signor to The Sewaren,

Original application 376,990. Divided and 11, 1933, Serial No. 65

10 Claims.

This invention relates to the manufacture of stannic chloride or the like, and has for its object improvements in the manufacture of stannic chloride. The invention contemplates, more particularly, an improved apparatus for manufacturing anhydrous stannic chloride and the like.

Anhydrous stannic chloride, or tetrachloride of tin (SnCli), as it is commonly designated, has heretofore been made by bringing metallic tin and dry chlorine gas into active relation with one another. The reaction may be indicated as follows:

Sn+2C12=SnCl4 l5 Metallic tin, in the form of bars or pigs, is placed in a closed vessel and chlorine gas is forced into the vessel. The reaction is exothermic, approximately 896 B. t. u. being generated per pound of tetrachloride of tin produced.

In order to reach any commercially feasible rate of production, it is necessary to have the largest possible surface area of tin exposed to the action of the chlorine gas, but, unless some means is employed to remove the heat generated, the tin soon melts and the exposed surface area of tin is so greatly reduced that production of tetrachloride of tin is reduced to a negligible rate. The heat of reaction is so great that, unless the heat is dissipated in some way, the temperature rises rapidly and the tin is soon heated to its melting point.

As the bars or pigs of tin are reduced in size, the danger of melting is increased because the ratio of surface area to Weight is increased. The molten tin, flowing to the bottom of the vessel, clogs such outlets as are used to Withdraw thetetrachloride of tin produced. Metallic iron is attacked by chlorine gas at elevated temper- 4o atures, and, since the reaction vessel employed is most conveniently and cheaply made of iron, there is danger that the vessel will be destroyed and that the tetrachloride of tin will be unduly contaminated, unless the temperature is carefully controlled.

In connection with this heretofore customary method of manufacturing tetrachloride of tin, it has been proposed to dissipate the heat resulting from the reaction by circulating the chlorine gas in the vessel through a series of cooling pipes located away from the zone of reaction, the pipes being cooled by Water or other suitable means. `'I'his is very ineicient because the chlorine gas has a low specific heat and is a poor conductor of heat. Moreover,l there are likely to Vulcan Detinning Company, N. J., a corporation of New Jersey July 9, 1929, Serial No.

this application January be dead air spaces or pockets among the bars or pigs of tin in the vessel that are not reached by the circulating chlorine gas, at which points melting of the tin readily occurs. For this reason it has been necessary to control the temperature 5i pensive commodity, are tied up, thus making nec- 15N essary a large capital investment. Tetrachloride of tin is, moreover, very volatile so that the larger the number or size of the vessels used, the greater will be the loss of tin in the form of vapor when the vessels are opened for recharging. This is 20 of special importance when the temperature is high, because the vapor pressures of the tetrachloride of tin and of the chlorine gas conned Within the reaction vessel increase rapidly with increasing temperatures.

It has also been proposed to manufacture anhydrous stannic chloride by'immersingv metallic tin in a liquid medium saturated with chlorine gas, .in which case the chlorine dissolved in the liquid reacts with the tin to form tetrachloride 30 of tin. The liquid medium suggested is the tetra# chloride of `tin itself. This method is commercially impracticable, because the tetrachloride of tin will only dissolve a comparatively small quantity of chlorine. The solubility of chlorine, 35 moreover, in such a liquid medium decreases rapidly as the temperature increases, so that as soon as the liquid becomes heated, due to the heat of reaction, the chlorine gas is liberated and rises to the surface of the liquid instead of re- 40v acting with the immersed tin. This uncombined gas accumulates in the reaction vessel, and, unless it is allowed to escape, it causes an increase in pressure in the vessel. The pressure, therefore, soon becomes dangerously high. If allowed to escape, not only is there a prohibitive loss of chlorine, but there is also carried off a considerable quantity of tetrachloride of tin vapor that can only be recovered With considerable difficulty.

It is, therefore, apparent that the heretofore` customary methods of manufacturing stannic chloride are not highly satisfactory, and that they at best leave something to be desired. In spite of the numerous efforts made to of small Vessels, have 10" improve these processes, they still remain highly inefficient, costly and dangerous.

In accordance with the practice of the present invention, the disadvantages of the foregoing methods are for the most part eliminated, and it is possible to attain a very large production of stannic chloride or the like in comparatively small vessels with no danger of melting the metallic tin employed, and with but slight losses of chlorine gas and tetrachloride of tin vapor.

According to the process of the present invention anhydrous stannio chloride is manufactured by bringing together metallic tin immersed in a liquid medium and chlorine gas,-the liquid medium preferably being one that is not affected by chlorine, that has a boiling point below the melting point of tin, and that will not react with the tetrachloride of tin produced. In addition to conducting the reaction in such a liquid medium, the following steps, alone or in combination, are contemplated: A portion of the liquid mixture is withdrawn from the zone of reaction and cooled, after which the cooled liquid is returned at least in part to the zone of reaction. The unconsumed chlorine gas that rises from the surface of the liquid medium is withdrawn and, if desired, cooled, after which it is returned to the zone of reaction. The liquid is brought to its boiling temperature, and vapor and chlorine gas are together withdrawn and cooled, the condensate and cooled gas being returned to the zone of reaction.

In the practice of this invention metallic tin, preferably in the form of bars, is placed in a closed reaction vessel provided with suitable outlets and inlets, after which a sufficient quantity of liquid is admitted completely to cover the tin. The liquid medium is preferably one that is not affected by chlorine, that will not react with the tetrachloride of tin produced, so as to impair its quality, and that has a boiling point below the melting point of tin. The preferred liquid is the tetrachloride of tin, although other liquids meeting the above requirements may be used, such, for example, as carbon tetrachloride (CCli). It is also possible to use a liquid medium having a boiling point higher than (or equal to) the melting point of tin, provided the temperature of the reaction mixture is carefully controlled, such as by sufficiently cooling the gas or liquid or both. Also, a liquid medium may be used which is affected by the chlorine, provided, however, that the reaction product is not one which contaminates the tetrachloride of tin produced. Chlorine gas is then admitted through an opening in the bottom of the vessel. In bubbling upwardly, the chlorine gas cornes in contact with the immersed metallic tin, reacting with the same to form tetrachloride of tin, in accordance with the equation set out above.

While much of the chlorine gas bubbling through the liquid medium reacts with the metallic tin, a considerable portion of the gas will bubble completely through the liquid without reacting. In accordance with the practice of the present invention, this unconsumed chlorine gas is returned to the bottom of the vessel, and reintroduced into the liquid medium.

Since the tin is at all times submerged in the liquid medium, and since the liquid medium itself has a boiling point lower than the melting point of tin, at least in the present preferred practice of the invention, no melting of the tin can occur. In case a liquid medium having a boiling point higher than (or equal to) the melting point of tin is employed, suicient cooling effects can be obtained to inhibit the melting of the tin.

In order to remove heat generated by the reaction, the liquid mixture within the vessel is, at least in part, advantageously withdrawn from the zone of reaction and passed through cooling pipes, the pipes being cooled by water or other suitable means. Cooling the liquid mixture is more efficient than cooling the chlorine gas, since the liquid mixture has a higher specific heat and is a better conductor of heat than is the chlorine gas.

It is also desirable, however, to circulate and cool the chlorine gas for at least two reasons: first, to obtain a still greater transfer of heat, and therefore, a greater production of tetrachloride of tin; and, second, to cool the chlorine gas and tetrachloride of tin vapor accompanying the chlorine, so as to condense as much of the tetrachloride of tin as possible, thereby reducing the amount of tin lost in the form of vapor when the vessel is opened for recharging.

According to a still further feature of the present invention, a liquid having a boiling point below the melting point of tin is used and the temperature in the reaction vessel is allowed to rise to the boiling point of the liquid. When this temperature is reached, the liquid vaporizes and heat is absorbed. The extent to which heat is absorbed may be illustrated as follows: The latent heat of vaporization of stannic chloride is about 84 B. t. u. per pound, and the heat of formation of stannic chloride is about 896 B. t. u. per pound.

It is, therefore, evident that the vaporization of about 10.6 pounds of tetrachlorine of tin will absorb the heat generated in the reaction producing one pound of the tetrachloride of tin. A very substantial cooling effect can therefore be obtained by conducting the process at the boiling point of the liquid medium or mixture employed.

In the practice of the foregoing feature of the present invention, the vapors of the distilled liquid, together with any unconsumed chlorine gas, are conducted into a condenser, Where the vapors are condensed. The condensate is returned, at least in part, to the chlorinating vessel, serving to maintain sufficient liquid in the vessel to keep the same at a normal operating level, the surplus being drawn off to keep the level from rising too high. The unused chlorine gas passes through the condenser where it is cooled, and is returned to the bottom of the vessel for reuse.

This method of removing heat from the zone of reaction is very efiicient, because the liquid vapors have a relatively high specific heat, and since they are at a comparatively high temperature, the heat transfer between them and the cooling medium is high. The temperature within the reaction vessel is, furthermore, automatically maintained at the boiling point of the liquid medium employed, which makes possible a high rate of production of tetrachloride of tin.

The invention will undoubtedly be better understood by reference to the accompanying drawings, taken in conjunction with the following description, in which:

Fig. 1 is a diagrammatic representation of apparatus adapted for the practice of the invention; and

Fig. 2 is a diagrammatic representation of a modified form of apparatus, also adapted for the practice of the invention.

The apparatus shown comprises a reaction vessel I0, preferably constructedof'metal, such as iron or steel.A AIn close'proximity to the reaction vesselis 'a heat-interchanger II. The reaction vessel" and heat-interchanger are connected by means `of a cooling coil I2, the coil connecting with the reaction vesselk at two places; just below the normal-liquid operating level I3 by means of conduit I4; and at or near the bottom of the reactionvessel by-means of conduit! I5.

:In addition to the cooling coil, the heat-inter'- changer comprises'a tank adapted to surround the cooling coil. By means of a valved pipe connection I6, regulated'amounts of water may be introduced into thetank, preferably at the bottom, and an ofi-take pipeV I'I, at or near the top of '-the' tank, is pro-vided for the withdrawal of wateri A pump (not shown) may advantageouslybefass'ociated with at least one of the conduits, preferably-the lower one, for circulating liquid from the reaction vesselthrough the .cooling coil. The-'reaction vessel comprises a main body portion equipped with a removable top I8. A` perforated platform |19 isV located at or nearthe bottom of the reaction vessel, adapted to support a load of metallic tin 20, preferably -in the form-of bars or pigs. The platform contains a large number of relatively' small holes, Vadapted to-disseminate small bubbles of chlorine gas. The bottom of the reaction vessel is equipped with a valvedv outlet 2| for the withdrawal of liquid. The bottom'of the vessel alsocontains afvalved inlet-22fadapted for the introductionof chlorine gas, and liquid (if desired).

A condenser 23 is in close proximity to the reaction vessel. It comprises a tank through which extends a cooling coil 24. A conduit 25 connects the upper end of the reaction vessel, above the normal liquid operating level, with the coolingcoil. A pump 26 is interposed between the conduit and thecooling coil. The conduit connects with the reaction vessel above the normal operating liquid level, so that unconsumed gas Yand vapor may be conducted from the vessel to the condenser. A Lconduit 2l connects with the cooling coil of the condenser and the lower end of thereaction vessel, preferably by means of the gas inlet 22. A valved water inlet 28, preferably atfor near the bottom, and an, oil-take pipe 28, at or near the top, are associated with the condenser tank 'for the introduction and withdrawal of; cooling water.

Referring more particularly to the modifiedY form of apparatus shown in Fig. 2, the conduit 25 connectingjthe reaction vessel and cooling coil 24 is not equipped with.l a pump. 4The pump 26 is located, instead, in the conduitv 21 which connects the reaction vessel at its lower end with cooling coil 24. A trap 28a is located between the pump and the ,cooling coil in order to collect condensate. This trap isl in turn connected with a pipeline 29a leading into the reaction vessel, and adaptedto convey condensate to the reaction vesselat a point aboveits normal operating liquid level. IAvvalved outlet 30 is provided in the pipe line for withdrawing condensate, .if desired. Y

The apparatus described above may be operated as follows in the practice of the invention: v To begin operations, the lid I8 is removed from the reaction vessel I0. An appropriate number of bars of metallic tin 20 are suitably piled on'the perforated platform I9. yWhile the valves in the outlet 2| and inlet 22 are closed, theliquid mediu'mcon'templated by the invention is'poured into the reaction vessel. In the present preferred practice of the invention, liquid tetrachloride of tin is itself employed 'as' the liquid medium. A sucient amount of the liquid is introduced into the vessel completely to immerse the bars of metallic tin, and to bring vthe height of the liquid in the vessel to the normal operating level I 3.H The lid I8 is then' clamped onto the reaction vessel.

AThe valve in the gas inlet 22 is then suitably opened, and chlorine gas is introduced into the reaction Vessel. The chlorine finds its way to the platform I9, where it is disseminated by the perforations to form a relatively large number of chlorine gas bubbles. These bubbles of chlorine rise upwardly among the bars of tin, and contact with the tin. The reaction between chlorine and tin indicated above then takes place to form tetrachloride of tin.

The heat of reaction is such that the contents of the reaction vessel promptly rise in temperature. Inv order to dissipate some of the heat in order to avoid overheating, various steps may be followed: Thus, for example, the liquid may be circulated throughv the heat-interchanger I I. This circulation may be eifected by thermal syphon action, or by means of a pump (not shown). The heated liquid is advantageously passed from the reaction vessel to the. cooling coil I2 through the pipe I4. The cooled liquid returns from the cooling coil to the reaction vessel through conduit I5. During the cooling operation, regulated amounts of cooling water are introduced into the heat-interchanger by means of the valved pipe I6. outlet pipe I 1. y

Referring more particularly to the operation to be conducted in the apparatus shown in Fig. l, the use of the heat-interchanger I| may be avoided, or not, or varied, as desired. While much of the chlorine gas bubbling upwardly through the liquid will react with the immersed metallic tin, a considerable portion of the gas will rise to and accumulate around the upper end of the reaction vessel. In order to cool the now highly heated chlorine gas, it is advantageously circulated through the condenser (or heat-interchanger) 23 by means of the conduit 25, pump 26, cooling coil 24, and return conduit 21. VDuring this cooling operation, regulated amounts of cooling water are introduced into the condenser by means of the valved inlet 28. Overflow water escapes by way of the outlet 29. The cooled chlorine gas is reintroduced into the reaction'vesjsel through the gas inlet pipe 22.

It is, of course, apparent that if the liquidl within the reaction vessel is heated to its boiling point, liquid vapor will accumulate together with the unconsumed chlorine gas at the upper end of the reaction vessel. This vapor is also circulatedy through the condenser. The cooling to which it is subjected reduces the vapor, at'

least for they most part, to a liquid condensate.

This condensate is preferably reintroduced into' the reaction vessel, together with the accom'- panying chlorine gas,-although it may be withdrawn from the system in Whole or in part.

The heat inter-'changer 'II and the condenser 23 may be made to work inter-dependently in orderto eect a control over temperaturelconditions within the reaction vesself A 'relatively large, or small, Aamount of the liquid maybe withdrawn from the reactionvessel, and circulatedA through the heat-interchanger II. l In fact,

The overilow Water escapes by way of thek 4 it may at times be advantageous not to circulate any of the liquid through the heat-interchanger. At the same time unconsumed hot chlorine gas is circulated through the condenser 23 for cooling.

As the immersed tin is converted to tetrachloride of tin, and the amount of liquid within the reaction vessel tends to increase in amount, suitable amounts of liquid may be withdrawn through the valved outlet 2l to keep the level of the liquid within the reaction Vessel at its normal operating level I3. Under accurately controlled operating conditions, the valve in outlet 2| may be adjusted to withdraw tetrachloride of tin substantially as fast as it is made.

The apparatus shown in Fig. 2 may be operated substantially like that shown in Fig. l and as justdescribed above. This form of apparatus is particularly adapted for the manufacture of anhydrous stannic chloride when the operation is to be conducted at boiling temperatures, and advantage is to be taken of the cooling effects obtained at such temperatures. In the apparatus shown, the mixture of unconsumed chlorine gas and liquid vapor are together circulated through the condenser 23. The condensed vapor collects in the trap 28a, from which it may be suitably returned to the reaction vessel or may be withdrawn in whole or in part from the system. The unconsumed but cooled chlorine gas, on the other hand, is conducted through the pump 2S and forced through the conduit 21 back into the reaction vessel.

It is, of course, to be understood that the examples of the practice of the invention just described are not to be taken as restrictive of the scope of the invention. To those skilled in this art, other variations of the practice of the invention will undoubtedly suggest themselves. The principles of the invention have a wider application than in the specic illustrations just outlined. This application is a divisional application of my copending application Serial No. 376,990, filed July 9, 1929, patented February 14, 1933, No. 1,897,360.

I claim:

1. In an apparatus for manufacturing anhydrous stannic chloride, the combination comprising a reaction vessel, a perforated platform disposed in the lower portion of the reaction vessel above the bottom thereof and adapted to support a charge of metallic tin, a condensercooler, a gas and vapor carrying conduit connecting the interior of the reaction vessel above its normal liquid level with the condenser-cooler for the withdrawal of gas and vapor from the reaction vessel, and a two-branch conduit connecting the condenser-cooler and the reaction vessel, one of said branch-es being provided with a sump for the collection of condensate and connecting with the interior of the reaction vessel at a point adjacent the liquid level therein for the return of condensed vapor to the vessel, the other of said branches connecting with the interior of the reaction vessel below its normal liquid level for the return of cooled gas.

2.'In an apparatus for manufacturing anhydrous stannic chloride, the combination comprising a reaction vessel, a heat-interchanger, a liquid carrying conduit connecting the heat-interchanger with the interio-r of the reaction vessel at or near its lower end below the normal liquid level of the reaction vessel, another liquid carrying conduit connecting the heat-interchanger with the interior of the reaction vessel below the normal liquid level of the reaction vessel but above the point of connection of the first conduit, whereby hot liquid may be removed from the vessel and be returned thereto after being cooled while passing through the heat-interchanger by thermo-syphonic action, a condenser-cooler, a, gas and vapor carrying conduit connecting the interior of the reaction vessel above its normal liquid level and the condenser-cooler for the withdrawal of gas and vapor from the reaction vessel, a two-branch conduit connecting the condensercooler and the interior of the reaction vessel, one of said branches being provided with a sump for the collection of condensate and connecting with the interior of the reaction vessel at or above its normal liquid level for the return of condensed vapor to the vessel, the other of said branches connecting with the interior of the reaction vessel below its normal liquid level for the return of cooled gases.

3. Apparatus for manufacturing anhydrous stannic chloride which comprises a reaction vessel adapted to contain a liquid, a condenser, means whereby gas and vapor may be withdrawn from the reaction vessel to the condenser, means whereby gas from the condenser may be introduced into the reaction vessel at a point below the liquid level within the reaction vessel, and means whereby condensate from the condenser may be introduced into the reaction vessel at a point adjacent the normal liquid level therein.

4. Apparatus for manufacturing anhydrous stannic chloride which comprises a reaction vessel adapted to contain a liquid, a heat-interchanger, thermosyphonic means whereby liquid may be withdrawn from the reaction vessel, cooled by circulation through the heat-interchanger, and returned to the reaction vessel, a condenser, means whereby gas and vapor may be passed from the reaction vessel into the condenser, and means whereby gas and condensate from the condenser may be introduced into the reaction vessel together at a point below the normal liquid level within the reaction chamber.

5. Apparatus for manufacturing anhydrous stannic chloride which comprises a reaction vessel adapted to contain a liquid, a heat-interchanger, thermosyphonic means whereby liquid may be withdrawn from the reaction vessel, cooled by circulation through the heat-interchanger, and returned to the reaction vessel, a condenser, means whereby gas and vapor may be passed from the reaction vessel into the condenser, means whereby gas from the condenser may be introduced into the reaction vessel at a point below the liquid level within the reaction vessel, and means whereby condensate from the condenser may be introduced into the reaction vessel at a point adjacent the normal liquid level therein.

6. Apparatus for manufacturing anhydrous stannic chloride which comprises a reaction vessel adapted to contain a liquid, a condenser. a conduit connecting the interior of the reaction vessel above the liquid level therein with the condenser, whereby gas and vapor may be withdrawn from the reaction vessel, and a two-branch conduit connecting the condenser and the interior of the reaction vessel, one of the branches being provided with a sump and connecting with the interior of the reaction vessel at a point adjacent the liquid level therein, whereby condensate may be collected and introduced into the reaction vessel, and the other of the branches connecting with the interior of the reaction vessel below the liquid level therein, whereby cooled unccndensed gases may be returned to the reaction vessel.

7. Apparatus for manufacturing anhydrous stannic chloride comprising a reaction vessel, a perforated platform disposed in the lower portion of the reaction vessel above the bottom thereof and adapted to support a charge of metallic tin, a condenser, and means connecting the reaction vessel and the condenser whereby gas and vapor from the reaction vessel may be passed into the condenser and gas and condensate from the condenser may be introduced into the reaction vessel.

8. Apparatus for manufacturing anhydrous stannic chloride comprising a reaction vessel, a perforated platform disposed in the lower portion of the reaction vessel above the bottom thereof and adapted to support a charge of metallic tin, a condenser, means connecting the reaction vessel and the condenser whereby vapor forming in the reaction vessel may be passed into the condenser and condensate forming in the condenser may be passed into the reaction vessel, a heat interchanger, and means connecting the reaction vessel and the heat-interchanger whereby liquid in the vessel may be withdrawn therefrom, cooled by circulation through the heat-interchanger and returned to the vessel.

9. Apparatus for manufacturing anhydrous stannic chloride comprising a reaction vessel adapted to contain a liquid, a condenser, a conduit connecting the reaction vessel at a point above the normal liquid level therein to provide for the passage of gas and vapor from the reaction vessel to the condenser, a conduit connecting the condenser and the interior of the reaction vessel at a point below the normal liquid level therein to provide for the introduction of gas from the condenser into the reaction Vessel below the surface of liquid therein, and a second conduit connecting the condenser with the interior of reaction vessel adjacent the normal liquid level therein to provide for the introduction of condensate from the condenser into the reaction Vessel adjacent the surface of liquid therein.

10. Apparatus for manufacturing anhydrous stannic chloride comprising a reaction vessel adapted to contain a liquid, a. perforated platform disposed in the lower portion of the reaction vessel above the bottom thereof and adapted to support a charge of metallic tin, a condenser, a conduit through which gas and vapor may pass from the reaction vessel to the condenser, means whereby gas and condensate from the condenser may be introduced into the reaction vessel, and a heat-interchanger capable of operating thermosyphonically associated with the reaction vessel, whereby liquid may be withdrawn from the reaction Vessel, cooled during passage through the heat-interchanger, and returned to the reaction 30 vessel.

WILLIAM J. BUT'IFIELD. 

